1. Field of the Invention
The present invention relates to a tape tension servo apparatus for use with a tape driving apparatus such as a video tape recorder (VTR) or the like.
2. Description of the Prior Art
There have heretofore been proposed tape tension servo apparatus which comprise a tape tension detecting means for detecting a tape tension, a tension comparing means for comparing a detected tape tension from the tape tension detecting means with a reference tape tension and a tape tension regulating means for regulating a tape tension in response to a compared output from the tension comparing means.
In the conventional tape tension servo apparatus, as shown in FIG. 1 of the accompanying drawings, when a reference tape tension is changed from a current tape tension N1 to a target tape tension N2, if there is a small difference therebetween, then a tape tension approaches the target tape tension N2 as shown by a broken curve a. After having passed the target tape tension N2 a little, the tape tension reaches the target tape tension N2 while being vibrated a little.
However, when the reference tape tension is changed from the current tape tension N1 to the target tape tension N2, if there is a considerably large difference therebetween, then the tape tension approaches the target tape tension N2 as shown by curve b in FIG. 1. After having passed the target tape tension N2 largely, the tape tension being vibrated considerably reaches the target tape tension N2 after a lot of time. As a consequence, when the reference tape tension is changed rapidly, the tape tension cannot follow the reference tape tension.